Gibson Deluxe Tuners (a weak design?)

Please note that this post is part one of four posts. I highly recommend reading all four posts in order before acting on any of the information.

The other parts are located here:

Part 2: http://diystrat.blogspot.com/2009/01/gibson-deluxe-tuners-part-two.html
Part 3: http://diystrat.blogspot.com/2009/02/gibson-deluxe-tuners-fix.html
Part 4: http://diystrat.blogspot.com/2010/01/gibson-deluxe-tuners-revisit.html

I have a problem with one of the tuners on my Les Paul. It had the problem already when I bought the guitar a few years ago and I managed to do a temporary fix, but the problem has resurfaced.

Before you continue, please note that this is written from an engineering point of view.

Firstly, let’s have a look at a typical stamped (open-backed) guitar tuner.

There are several components and many names for those components, so my apologies if I use ones that you are not accustomed to. Firstly, the tuner can also be called the tuning head, tuning peg, or the machine head (and possibly other names). It has a main plate, through which the main cylinder (or capstan), passes. The capstan is the shaft that the string itself passes through. On the end of the capstan is a gear, sometimes called the pinion gear, and a screw/bolt holds that on to the end of the capstan. Then we have another shaft or pin with the tuner knob (or button) on the end of it. This pin has a gear on it too (in fact they are one part in most cases), and this particular gear is known as a worm gear. From now on I will just refer to this shaft as the worm gear.

As an aside, and for any non-engineer-minded people out there, the reason a worm gear is used is because turning the button/knob will rotate the worm gear, which will in turn rotate the pinion gear and the capstan, thus tightening or loosening the string, whereas no matter how much you tighten the string, the pinion gear cannot force the worm gear to turn. This is a really good way to keep strings in tune without making it really hard to turn the knob.

OK, back to the description of the tuner. There is one further feature that I have not yet mentioned and that is the retaining “claws” which are part of the main plate and hold the worm gear in place. The claws stop the worm gear from moving away from the pinion gear or falling away from the main plate. The plate stops the worm gear from falling against the guitar and the pinion gear stops it from falling out in the direction of the capstan. So hopefully you can see that the worm gear cannot possibly fall out unless the pinion gear is removed.

Now to the Gibson Deluxe Tuners (and why I think they are a weak design).

As you can see, the tuner has the same components as any standard open-backed tuner, but please note one subtle difference – although the claws stop the worm gear from moving away from, or towards the pinion gear (i.e. from side to side), they don't stop it from falling away from the main plate. Seriously, it can just fall right off.

“But wait!”, I hear you Gibson Deluxe Tuner fans shouting, “The Gibson Deluxe Tuners have a back cover which stops the worm gear from falling away from the main plate!”

Well, you are correct, but this leads me to the problem with my tuner... the back cover has fallen off. And this brings me to my second criticism of Gibson Deluxe Tuner design. You would think that, if the back cover was the only thing holding the worm gear in place, it would be held on in a way that would be very hard to move.
Let’s have a look at their design.

The back cover is held on with two little tabs (one of mine is slightly damaged, but this happened while I was trying to find a solution to keeping it in place. It originally fell off with the tabs intact). Now as an engineer, I would think that a tab should at least fold over to keep something in place, but these ones just go into slots and do not appear to be twisted, folded, or in any other way modified once they go through the slots. In other words they are held in by “interference fit” only, so that they can come out just as easily as they went in (edit: actually, this isn't 100% correct - they are "staked" in place [see the comments at the end of this post], although that doesn't add much strength in the direction they would fall off ). Now let’s think about what’s on the end of the worm gear. That’s right, a big knob/button that sticks out and is basically on the end of a lever. What do we often use levers for? Well, for prising things out of place for one. The longer the lever, the easier it is. So one accidental knock on the tuning knob and you can dislodge the back cover, letting the worm gear fall out of place.

In the course of trying to find a single replacement Gibson Deluxe Tuner (which, not surprisingly, cannot be bought separately), I have noticed many other people scrambling to buy single replacements off ebay or asking if anyone has a spare one on musicians’ forums. A full set is not cheap either; around £60 would not be unusual. I wouldn’t even mind paying that if I though it was a good strong design, but I think you can guess by my rantings how much I think of these things. Unfortunately replacing them with anything other than originals devalues the guitar, so there isn’t much choice.

Additionally, on the front face of the guitar head you need to use a bushing (also called a ferrule) which stops the capstan from rubbing on the wood of the guitar when it is being rotated, and whereas these are normally press-in bushings on tuners of similar design to Gibson Deluxe Tuners, on the actual Gibson ones, they are screw-in bushings. Now I have no complaints about this, design-wise, I’m just saying that there are very few replacements available other than the Gibson Deluxe Tuners.

Gibson Deluxe Tuner bushing (and washer)

Standard bushing

So stay tuned (no pun intended) for the next blog post, where I will try to fix mine.